The present invention relates to a sound-field production apparatus. More particularly, the present invention relates to a sound-field production apparatus for reproducing a sound-field space having an effect of sound-image broadening by consideration of sounds reflected by surroundings.
An AV amplifier designed in recent years is capable of reproducing a sound field that gives a better feeling of presence on the scene at a home by virtue of signal processing carried out by a DSP (Digital Signal Processor) and by addition of actually measured reverberation characteristics of a movie theater and a theater for respective signals of typically a 5.1 channels, that is, L (left), C (center), R (right), SL (surround left) and SR (surround right) channels plus an LFE0.1 channel. Examples of such a product and an environment are an AC (Audio Coding) 3 made by Dolby Corporation and a dts (Digital Theater System) produced by DTS Corporation. Such a conventional system employs a multi-speaker output unit comprising a plurality of speakers such as the L, C, R, SR and SL speakers, and adds reflected and reverberated sounds to outputs of the speakers on the basis of measured data such as a virtual sound source distribution diagram of a movie theater being revived.
Even if reverberation characteristics obtained from measured data as described above can be reproduced with a high degree of fidelity, however, it is by no means possible to render effects of a sound field as exhibited by natural blending of sounds and pictures peculiar to a movie theater or the like. This is because, in the case of a movie theater, a front speaker is located behind a screen in an arrangement different from that of an ordinary home wherein a front speaker is located at a place in front of a monitor screen.
When a sound source generates a sound at a place in front of the listener at a distance of at least about 1 meter from the listener in an anechoic room, the listener is almost incapable of feeling separation from the sound source by a distance independently of what place the sound source is located. In an echoic room, on the other hand, the listener is capable of feeling separation from the sound source by a distance in dependence on the position of the sound source. This latter fact indicates that, in the case of a sound source separated away from a human being by a distance of at least about 1 m, the human being can be said to feel separation from a sound source by a distance due to existence of sounds reflected by a wall and/or a floor.
In an actual movie theater, a front speaker is located in a space behind a screen. A playback sound comprises a sound output by the front speaker to reach the listener through the screen and the sound reflected repeatedly by a rear wall and side walls, which exist in the rear space behind the screen, and by the screen under a variety of conditions. The reflected sound is further affected by a number of holes provided above the screen.
FIG. 6 is a diagram showing a typical screen sound-transmission characteristic of a sound screen. The screen sound-transmission characteristic was obtained as a result of a measurement by using a measurement microphone located in front of a speaker at a distance of 1.25 m with a distance from the speaker to the sound screen inserted into a location in front of the speaker set at 42 cm.
As described above, the conventional sound-field production apparatus adopts a multi-speaker system, and is capable of reproducing a sound field that gives a better feeling of presence on the scene at a home by addition of actually measured reverberation characteristics of a movie theater and a theater. Nevertheless, the conventional sound-field production apparatus has a problem of impossibility to render effects of a sound field as exhibited by natural blending of sounds and pictures peculiar to a movie theater or the like.
It is thus an object of the present invention addressing the problem described above to implement a sound-field production apparatus capable of reproducing an impressive sound field that gives a better feeling of presence on the scene as a sound field in a movie theater or the like does by creating a sound-field space having an effect of sound-image broadening through adoption of a relatively simple method.
In order to achieve the object described above, the present invention provides a sound-field production apparatus wherein some additional sounds to serve as substitutes for representatives of sounds reflected by a sound screen, a wall, a floor and the like are each generated by an auxiliary sound source at a timing lagging behind a direct sound generated by a main sound source and at a level lower than the direct sound, and the additional sounds are added to the direct sound, so as to arouse a feeling of separation of the sound source and the sound screen from the listener at apparently longer distances exceeding the actual distances to the sound sources and the sound screen.
As a result, it is possible to implement a sound-field production apparatus capable of reproducing a sound field that gives a better feeling of presence on the scene by creating a sound-field space having an effect of sound-image broadening through adoption of a relatively simple method.